The semiconductor fabrication industry continues to need metal source containing precursors for chemical vapor deposition processes including atomic layer deposition for fabricating conformal metal containing films on substrates such as silicon, metal nitride, metal oxide and other metal-containing layers using these metal-containing precursors. To this end, a method for preparing metal source containing precursors with a yield that is higher relative than previous preparation methods and, in certain instances, a cost that is lower than previous methods would be desirable to the semiconductor fabrication industry. Also desirable is a method for preparing these precursors whereby the metal source containing precursor is prepared while minimizing potential metal impurities that may be introduced during the preparation process, such as but not limited to, lithium, sodium, potassium and combinations thereof.
Previous methods for preparing polydentate β-ketoiminate ligands were performing using well known procedure such as the Claisen condensation of a bulky ketone and an ethyl ester in presence of a strong base such as sodium amide or hydride, followed by another known procedure such as Schiff base condensation reaction with alkylaminoalkylamine such as that shown below in the multi-step scheme depicted below as Equation 1:

Another method for preparing the metal-containing complexes involved reacting tridentate β-ketoiminate ligands with group 2 metal in the presence of ammonia, metal amide, metal hydride, or metal alkoxide such as that shown below in Equation 2.

The metal-containing complexes can also be prepared via reacting the polydentate β-ketoiminate ligand with alkyl lithium or potassium hydride to provide the lithium or potassium salt of the ligand, then followed by reaction with a metal halide having the formula MX2 (X═Cl, Br, I) such as that shown below in Equation 3:

However, the reaction such as Equation 2 using group 2 metals in the presence of ammonia may not be suitable for larger scale processing because bubbling ammonia is tedious process and the reaction yields are typically very low. Further, reactions such as Equation 1 and 3 involving sodium or potassium hydride as reagents are undesirable because of their high reactivity which can cause potential fire in addition to sodium or potassium impurities in the final product. Still other reactions that employ metal amides or alkoxides as reagents such as Equation 2 are not practical because the reagents are too expensive.